1. Field of the Invention
The present invention relates to a metal-containing ABS resin composition having superior impact and outer appearance.
2. Description of the Prior Art
As methods for imparting a metallic outer appearance to the surface of an ABS resin, various techniques are known such as metallic coating, hot stamping, wet plating and dry plating. However, these techniques are applicable only to formed resin products and involve complicated procedures.
If a metallic appearance is imparted to the resin itself, it is possible to obtain a formed resin product having a metallic outer appearance simply by a molding process without the after treatment of the formed resin as mentioned above, whereby the process for the production can be simplified. In this respect, various methods for incorporating metal powder in a resin have been proposed. For instance, there have been proposed a method in which at least 5% by weight of a metal powder is incorporated in an ABS resin to form pellets, which are then metallized with a metal and the like (Japanese Unexamined Patent Publication No. 97674/1979), and a method in which aluminum and copper or a copper alloy are added to a synthetic resin in an amount of from 1 to 80% by weight (Japanese Unexamined Patent Publication No. 114534/1979). However, formed ABS resin products having a metallic outer appearance obtained by these methods have drawbacks such that firstly, the formed resin product containing the metal powder presents a poor metallic texture on its surface and the color tone is rather dark, and secondly, when the resin is subjected to injection molding, the weld lines appearing on the surface of the formed product will be distinctly noticeable.
The weld lines are inevitably formed more or less during the injection molding of the ABS resin, and they are scar-like defects formed at positions where the molten resin flowing in the mold in separate streams along the passages of the mold gets together again to fuse. Namely, as the temperature of the front ends of the molten resin streams separated along the mold passages lowers, the mixing of the resin tends to be difficult when the separated resin streams get together to fuse, whereby defectively fused sectional surface appears on the surface of the molded product. Especially, the ABS resin containing a metal powder has a higher heat transmission rate than the ABS resin, and the temperature drop of the molten resin flowing in the mold is accordingly quicker, whereby the formation of the weld lines is more likely to occur.